From August 2006 to March 2010, Neptune continues its motion through Capricornus, the Sea-Goat, where it has been situated since early 1998. From March 2010, Neptune enters the constellation of Aquarius, the Water Carrier. The planet enters Pisces, the Fishes, in April 2022 where it will remain until 2039.

Neptune reaches opposition to the Sun (when it is closest to the Earth and brightest in the sky for the year) every 367½ days on average, i.e. about 2½ days later in each successive year. The apparent magnitude of the planet varies little during the period shown in the star chart - from +7.8 (at opposition) to +8.0 (at superior conjunction).

In 2010, Neptune will complete its first orbit since it was discovered on September 23rd, 1846. The planet will again be seen at its 1846 position in the sky (i.e. at the same longitude measured relative to the Earth) in mid-April 2009 (moving direct), in mid-July 2009 (moving retrograde) and again in early February 2010 (moving direct). Neptune will return to its discovery position in its orbit (i.e. at the same longitude measured relative to the Sun) in late June 2010.

Neptune will cross the celestial equator in Pisces in April 2026 (heading North-eastwards and moving direct), in August 2026 (moving retrograde and temporarily heading South-westwards) and again in January 2027 (resuming North-easterly motion, moving direct). For the first time in over 81 years, the planet will then become visible for a longer period of time in the Northern hemisphere than in the Southern hemisphere (it last crossed the celestial equator - as it headed Southwards along the ecliptic - in Virgo in 1944).

Looking further ahead, the planet will continue its Northward motion along the ecliptic until it reaches its most Northerly point in Gemini in 2067, having crossed its perihelion point (i.e. its closest point to the Sun; in this case 29.81 Astronomical Units or 4.46 thousand million kms) in Aries in 2046.

 [Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]

Twins Reunited

Further to the North-east (moving through Aquarius and, from 2009, through Pisces) is Neptune's planetary neighbour and 'twin'- Uranus. Seen from the viewpoint of the Earth, faster-moving Uranus 'overtook' Neptune when the two planets were in Sagittarius in July 1993 (at which point they were in conjunction, i.e. at the same celestial longitude). This was the first time the two planets had been seen at conjunction since they were discovered (Uranus in 1781, Neptune in 1846). Conjunctions of these two planets are rare events, taking place about every 172 years; the next one will be in the year 2164.

Finding Neptune from 2006 to 2023

Through to March 2010, pale-blue Neptune is located in the Eastern half of Capricornus. To find Capricornus, first locate the asterism (star pattern) unofficially known as 'The Steering Wheel', near the Northern border of Aquarius ('The Steering Wheel' is found by looking West of the Circlet of Pisces, which itself is found by looking South of the Great Square of Pegasus! For a star map of this region, see the Uranus 2006-2019 page).

The 'Steering Wheel' asterism, together with its nearby star Sadalmelik (also known as Aqr or Alpha Aquarii, apparent magnitude +2.9) is the most recognisable feature of Aquarius. A 'star-hop' will be required from 'The Steering Wheel' and Sadalmelik to the star Sadalsuud ( Aqr or Beta Aquarii, also magnitude +2.9) and then Southwards to the star Deneb Algiedi ( Cap or Delta Capricorni, magnitude +2.9) in the tail of Capricornus. Note that the stars Sadalmelik, Sadalsuud and Deneb Algiedi form an inverted triangle, which should help with the star-hopping procedure. When at Deneb Algiedi, you are within only a few degrees of Neptune, after which a larger-scale finder chart will be needed to pinpoint the planet precisely using binoculars (of which, see below). Also marked on the star map are the stars Cap (Nashira or Gamma Capricorni, mag. +3.6) and  Cap (Iota Capricorni, mag. +4.2), both of which should help in pinpointing the planet when using finder charts.

From March 2010, Neptune enters Aquarius, wherein the planet can be found by star-hopping Southwards from 'The Steering Wheel' asterism and Sadalmelik.

From April 2022, Neptune enters Pisces, whose most recognisable feature is the asterism known as the Circlet of Pisces. The planet will be situated to the South of the Circlet, whereby a star-hop will be required, with the assistance of a finder-chart.

Around all opposition dates shown on the star map, Neptune will be due South at local midnight in the Northern hemisphere (due North at local midnight in the Southern hemisphere).

Finding Finder Charts for Neptune on the Web

The above star chart is unlikely to prove sufficient to locate the planet, and a larger scale finder chart - showing a smaller area and fainter stars - will probably be required.

Accurate finder charts for locating Neptune are published on a variety of websites, such as Paul Money's AstroSpace site and the Royal Astronomical Society of New Zealand (in this case the available star chart shows the Southern hemisphere view, with South up and East to the right; they will need to be inverted for the Northern hemisphere view). Northern hemisphere charts for the current year can usually be found at the Sky & Telescope website by performing a search there on finding Neptune and clicking on the appropriate result. Charts at other websites can be found by using the following search engines (be sure to check the correct orientation of any chart found; it will need to be orientated North-up for Northern hemisphere observers and South-up for Southern hemisphere observers):-

Positions of the Superior Planets:

Current Position of the Sun and the Brighter Naked-Eye Planets (Star Map)

Credits

• The star chart was compiled using a variety of sources, including the commercial software 'MegaStar' (by Willmann-Bell, Inc) and the freely-downloadable SFA Star Charts by Dan Bruton. Star colours were based on those shown in "Patrick Moore's Colour Star Atlas" (Mitchell Beazley Publishers Ltd., London, 1973).
• The date of Neptune's perihelion point crossing was determined using the SkyGazer Ephemeris utility by John Biondo. Dates of constellation boundary crossings were determined using MegaStar.
• The future conjunction date of Uranus and Neptune was calculated using the 'Sky Diary' facility of the commercial software RedShift 5 by Maris Technologies Ltd.

Copyright © Martin J. Powell  Dec 2006; minor update Jan 2008

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